1. Technical Field
This invention relates generally to oil seals of the type having a carrier, a wear sleeve, and a sealing disk unitized in a single assembly, and more particularly to such seals wherein the sealing disk component has a pair of annular sealing lips that engage the wear sleeve in such manner that one of the lips retains lubricant on one side of the seal and the other lip excludes contaminants on the other side of the seal.
2. Related Prior Art
Unitized oil seals are commonly used in various mechanical devices wherever one component rotates in a bearing relative to an adjacent stationary component. The seal operates to close an annular space between the components in order to retain lubricant on the bearing side of the seal and exclude contaminants on the exterior side of the seal, to protect the bearing.
U.S. Pat. No. 4,484,752, which is owned by the assignee of the present invention and its disclosure incorporated herein by reference, discloses a unitized oil seal assembly having a pair of discrete sealing disks fixed side-by-side on the carrier to provide a pair of annular sealing lips that sealingly engage the wear sleeve. One lip serves as the oil-retaining seal and the other lip serves as the contaminant-excluding seal. While such oil seal assemblies perform satisfactorily, the requirement for two sealing disk elements adds cost and complexity to the manufacture of such assemblies. When fully assembled with the wear sleeve, the lips of the disks are bent in opposite axial directions. Special care must be taken to support the lips during assembly to assure that the lips maintain their oppositely bent orientation, further complicating the manufacture of such seal assemblies.
U.S. Pat. No. 5,462,287 discloses an oil seal having a single disk element whose inner free edge is split into two relatively thinner annular lip sections that serve as the oil-retaining and contaminant-excluding lips of the seal assembly. Splitting the inner free edge of the disk necessarily decreases the effective thickness of the oil-retaining lip, which may not be desirable in some applications where the oil-retaining lip is subject to wear. Additionally, the disclosed seal assembly utilizes the split side of the oil-retaining lip as the working surface in contact with the wear sleeve, making it more difficult to provide the usual hydrodynamic grooves or formations on the working surface of the oil-retaining lip. Special care must be taken to assure that the lip sections are bent in opposite axial directions, which adds cost and complexity to the assembly process and makes the root of the split prone to possible tensile forces and premature wear or tearing.
U.S. Pat. No. 5,615,894 discloses a non-unitized oil seal having a single sealing disk whose inner free edge is split to provide oil-retaining and contaminant-excluding lip portions. Special dies and forming steps are required to emboss hydrodynamic ribs on the contacting surfaces of both lip sections, which adds to the cost and complexity of the manufacture of such seals. The lip sections are also bent in opposite axial directions, and thus this seal assembly shares the same draw backs as those described previously.
Other unitized oil seal assemblies are known to include a PTFE sealing disk element having a conical configuration rather than the usual flat wafer configuration. The conical disk is bonded to the carrier by an annular rubber mounting collar. The collar encircles the disk at a location between its ends and supports the ends in sealing engagement with the wear sleeve to serve as the oil-retaining and contaminant-excluding lips of the seal. Such conical sealing disks are costly in comparison to traditional flat wafers and add to the complexity of making such seals, as does the need for the rubber mounting collar.